Apparatus for preventing the leakage of paint through a screen



Ap 1967 J. B. VAN DER WINDEN 3,313,232

APPARATUS FOR PREVENTING THE LEAKAGE OF PAINT THROUGH A SCREEN Filed Sept. 11, 1964 3 Sheets-Sheet l JNVENTOR. JOHANNES B. VAN DER WINDEN ATTORNEYS.

J. B. VAN DER WINDEN 3,313,232 APPARATUS FOR PREVENTING THE LEAKAGE OF April 11, 1967 PAINT THROUGH A SCREEN I5 Sheets-Sheet 2 Filed Sept. 11, 1964 INVENTOR. JOHANNES B. VAN DER WINDEN AMA/7F ATTORNEYS.

J. B. VAN DER WINDEN 3,313,232 APPARATUS FOR PREVENTING THE LEAKAGE OF April 11, 1967 PAINT THROUGH A SCREEN w 3 Sheets-Sheet :5

Filed Sept. 11, 1964 N M wf S RN Y I E WW W R HE m D T IN A A a V B. a S E N M WE J pmmxmm w QE United States Patent 3,313,232 APPARATUS FOR PREVENTING THE LEAKAGE 0F PAINT THROUGH A SCREEN Johannes Bernardus van der Winden, Amstelveen, Netherlands, assignor to Gebr. Stork & Cos Apparatenfabriek N .V., Amsterdam, Netherlands Filed Sept. 11, 1964, Ser. No. 395,379 Claims priority, application Netherlands, Sept. 12, 1963, 297,818 1 Claim. (Cl. 101118) My invention relates to a method for preventing the leakage of paint through a cylindrical screen in a screen printing machine. Up to the present there were few remedies against such leakage, and it could only be prevented either by stopping the supply of paint to the squeegee in good time or by cleaning the exterior of the screen. Both methods involve great drawbacks, which in practice caused inevitable losses of paint and of a proportion of the material to be printed upon.

It is a first object of my invention to provide for a method which does not involve any complication for the operators and which gives an automatic prevention of the leakage of paint through the screen. This object is achieved in that the screen is driven continuously even when one or more elements of the machine are stopped. This means that either when the cooperation between a screen and the material to be printed upon is interrupted or when the machine is stopped altogether, the screen continues to rotate at a given rate, in consequence of which no paint accumulates locally inside the screen and might leak through owing to gravity.

My invention further aims to provide a screen printing machine comprising a moving surface for supporting the material to be printed upon, and also comprising one or more cylindrical screens adapted to cooperate with the supporting surface, said machine being adapted for carrying out my method described above.

My invention will be explained in greater detail by reference to the drawing, in which an embodiment of the screen printing machine is illustrated.

FIG. 1 is a diagrammatic side view of the Whole machine.

FIG. 2 is an enlarged View, partly in section, of the lefthand part of the machine according to FIG. 1.

FIG. 3 is a section along the line IIIIII in FIG. 2.

FIG. 4 is a longitudinal section of a squeegee along the line IV1V in FIG. 2.

As can be seen in FIG. 1, the screen printing machine consists of a frame 1, on which is arranged an endless belt 2, which is adapted to travel in a continuous path between a driving pully 3 and an idler pulley 4. In the operative path 5 this belt 2 forms a surface for supporting the material 6 to be printed upon, which is unrolled from a supply roll, not shown. Mounted on the frame 1 is a driving motor 7, which transmits the driving force via a connecting rod 8 to the pulley 3. Above the path 5 are provided a number of bearing devices 9 for cylindrical screens 10. The material 6 printed upon is delivered, on the side of the machine to the left of FIG. 1, to an apparatus, not illustrated, for the further treatment of this material. On the underside of the continuous path traversed by the belt 2 a device 11 for washing the belt, a tension device 12, and a device 13 for applying an adhesive layer on the belt 2 are present, so that after passing around the idler 4 this belt can support the material 6 to be printed upon and grip it temporarily. After the material 6 has been released at the end of the machine to the left of FIG. 1, the remnants of adhesive are removed from the belt 2 by means of the washing device 11.

FIG. 2 shows the driving gear of the machine in greater 3,313,232 Patented Apr. 11, 1967 detail. Via the connecting rod 8 and a conventional universal joint 14 a gear wheel 15 mounted on a shaft 16 is driven. This gear wheel meshes with a partially shown gear Wheel 17, which is freely rotatable on a lay shaft 18. The gear wheel 17 meshes with a gear wheel 19 mounted on a short shaft 20, while the latter gear wheel in turn meshes with a gear Wheel 21 which is freely rotatable on a shaft 22. Mounted rigidly on this shaft is an element 23, which on one side forms a gear wheel 24 and on the other side, a clutch housing 25 enclosing the movable part of a clutch 26, which is adapted to establish a connection between the shaft 22 and the gear wheel 21.

Mounted on the short shaft 20 is a second gear wheel 27, which can be linked via a clutch 28 with the gear wheel 19. Furthermore on the lay shaft 18 a clutch element 29 is rigidly mounted, which element can be linked via a clutch 30 with the gear wheel 17. Mounted also on this lay shaft is a worm 31, which meshes with a Worm wheel 32, which is linked with the driving pulley 3 for the belt 2.

The clutches 26, 28, and 30 can be operated hydraulically with the aid of a cont-r01 valve 33, provided with an operating knob 34. The pressure medium required for this is supplied by a gear pump 35, which is driven by the shaft 16 and which sucks oil from a reservoir 36.

The shaft 22 is linked to a stub axle 38 via a socket 37 with a key joint. This stub axle forms part of the first bearing device 9 for a screen 10. Mounted on this axle 38 is a worm 39, which meshes with a worm wheel 49, mounted on a common shaft with a gear wheel 41. This gear wheel meshes with an idler wheel 42, which in turn meshes with teeth 43 on one end of the screen 10. This driving gear forms the subject-matter of, and is described in greater detail in copending patent application Ser. No. 395,656, filed Sept. 11, 1964.

In FIG. 3 the details of the just described driving gear are better visible, and the teeth 43 are present on a sleeve 44, which carries the corresponding end of the screen 10.

In FIG. 2 the belt 2 is not in contact with the screens 10. The situation in which it is in contact with the screens 10 is shown in FIG. 1, and for this purpose the belt 2 is forced upwards with the aid of as many rolls .5 as there are screens 10. These rolls 45 are supported in bell crank levers 46, which are adapted to pivot at 47 about a pivot rigidly mounted in the frame of the machine. The bell crank levers 46 are adjusted by means of a rod 48 which is pivotally connected with a rod 49 (see FIG. 1). The position of the rod 49 is conditioned by a hydraulic cylinder 50. This feature forms the subject-matter of copending patent application Ser. No. 395,880, filed Sept. 11, 1964, Patent No. 3,291,044.

FIG. 4 further gives a view of a screen 10 with a squeegee 51 therein, and supported at its two ends by a suspension element 52, the length of which can be adjusted and which is mounted pivotally in the bearing device 9.

The coordinated driving gear for the movement of the belt 2 and the rotation of the screen 10 is formed by the elements 15 to 43 illustrated in FIG. 2. The operating member of this driving gear is formed by the knob 34, by means of which the control valve 33 is turned. FIG. 2 shows the clutches 28 and 30 in open position so that cooperation between the belt 2 and the screen 10 is interrupted, and the drive of the belt 2 is disconnected. The rotation of the screen, however, continues, since pressure medium is fed by the control valve 33 to the clutch 26, so that via the stub axles 38 each of the screens 10 is driven continuously.

It will be evident from the foregoing description that my invention furnishes a solution for a problem of importance in machines of this type, viz. the prevention of leakage through a screen during a temporary stoppage of 3 the machine or some other interruption of the operation. The continuous rotation of the screens prevents the paint from settling by gravity to one region inside the screen and causing gradual leakage at a point.

What I claim is:

A screen printing machine comprising a surface for supporting material to be printed upon, a cylindrical printing member disposed adjacent said surface and having a screen extending completely therearound for continuously printing on material supported by said surface throughout each complete and successive revolutions of the printing member, means for relatively moving said surface and said printing member into and out of operative engagement with each other, means for normally continuously moving said surface longitudinally, means for rotating said screen for operative cooperation with said surface as the latter is moved longitudinally, continuously operated drive means including a pair of clutches respectively connected with said surface moving means and said screen rotating means, and means for controlling said clutches selectively for continuously driving said screen rotating means to continue rotation of said screen and disconnecting said surface moving means when said first mentioned means is operated to disengage said surface and said screen, whereby to prevent settlement of printing fluid in and dripping from said screen when the printing operation is stopped.

References Cited by the Examiner UNITED STATES PATENTS 444,412 1/1891 Lietze 101-115 X 2,017,010 10/1935 Meisel et a1 101182 2,928,340 3/1960 Stein et a1 101120 3,252,415 5/1966 Crawford 101182 X ROBERT E. PULFREY, Primary Examiner.

H. P. EWELL, Assistant Examiner. 

